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| United States Patent |
5,258,777
|
|
DeJager
, et al.
|
November 2, 1993
|
Thermal printer system with a high aperture micro relay lens system
Abstract
A thermal printer system using a multiple line scanning printhead with a
micro relay lens system having high numerical apertures on both object and
image sides.
| Inventors:
|
DeJager; Donald (Rochester, NY);
Baek; Seung-ho (Pittsford, NY)
|
| Assignee:
|
Eastman Kodak Company (Rochester, NY)
|
| Appl. No.:
|
749394 |
| Filed:
|
August 23, 1991 |
| Current U.S. Class: |
347/258 |
| Intern'l Class: |
B41J 002/435; G02B 013/24 |
| Field of Search: |
359/757,679
346/76 L,107 R,108
|
References Cited
U.S. Patent Documents
| 4080048 | Mar., 1978 | Kimura | 350/214.
|
| 4130350 | Dec., 1978 | Koizumi | 350/216.
|
| 4206974 | Jun., 1980 | Maeda | 350/215.
|
| 4235520 | Nov., 1980 | Kimura | 359/757.
|
| 4251131 | Feb., 1981 | Tojo | 350/414.
|
| 4364644 | Dec., 1982 | Ikemori | 350/464.
|
| 4368957 | Jan., 1983 | Chirra | 350/469.
|
| 4505553 | Mar., 1985 | Asoma | 350/414.
|
| 4514049 | Apr., 1985 | Hirano | 359/679.
|
| 4521086 | Jun., 1985 | Kurita | 350/464.
|
| 4537472 | Aug., 1985 | Asoma | 350/414.
|
| 4563060 | Jan., 1986 | Yamagishi | 350/414.
|
| 4591243 | May., 1986 | Yamagishi | 350/414.
|
| 4753522 | Jun., 1988 | Nishina et al. | 350/470.
|
| 4955701 | Sep., 1990 | Kataoka et al. | 350/481.
|
| 4999648 | Mar., 1991 | Debesis | 346/107.
|
| 5039212 | Aug., 1991 | Kanoshima | 359/679.
|
| 5053791 | Oct., 1991 | Baek et al. | 346/76.
|
| Foreign Patent Documents |
| 0276865 | Aug., 1988 | EP | 359/757.
|
Primary Examiner: Fuller; Benjamin R.
Assistant Examiner: Bobb; Alrick
Attorney, Agent or Firm: Short; Svetlana Z.
Claims
We claim:
1. A thermal imaging apparatus comprising:
an imaging drum arranged to mount a receiver member and a donor member in
superposed relationship thereon;
means for rotating the drum about an axis;
means for generating a plurality of modulated coherent light beams and;
light projection means for projecting said light beams onto said donor
member to transfer an image onto said receiver member by transfer of a dye
from said donor member;
wherein said light projection means includes a finite conjugate lens system
having high numerical apertures of at least about 0.2 on both object and
image sides and said lens system includes an aperture stop located
approximately at a center of said lens system and a plurality of lens
elements centered on an optical axis and arranged into two lens groups of
positive power to provide said high numerical apertures on both object and
image sides of said lens system.
2. The imaging apparatus of claim 1 and wherein said numerical aperture on
the image side is 0.5 or larger.
3. A thermal imaging apparatus comprising;
an imaging drum arranged to mount a receiver member and a donor member in
superposed relationship thereon;
means for rotating the drum about an axis;
means for generating a plurality of modulated coherent light beams and;
light projection means for projecting said light beams onto said donor
member mounted on said drum member to transfer an image onto said receiver
member by transfer of a dye from said donor member;
wherein said light projection means includes a finite conjugate lens system
having high numerical apertures on both object and image sides, an
aperture stop is located approximately at a center of said lens system and
a plurality of lens elements are centered on an optical axis and arranged
into two lens groups of positive power to provide said high numerical
apertures on both object and image sides of said lens system, one of said
lens groups being located on one side of said aperture stop and another of
said lens groups being located on another side of said aperture stop, said
lens groups each comprising an outer-most lens element and an inner-most
lens element located in close proximity to said aperture stop, said
inner-most lens element of each lens group having a convex surface facing
towards said aperture stop.
4. The imaging apparatus of claim 3 and wherein said numerical apertures
are at least 0.2.
5. The imaging apparatus of claim 4 and wherein said numerical aperture on
the image side is 0.5 or larger.
6. An imaging apparatus comprising:
means for supporting an imaging member that is to receive an exposure;
means for generating a light beam; and
light projection means for projecting said light beam onto said member,
wherein the light projection means includes a finite conjugate lens system
having high numerical apertures on both object and image sides of at least
about 0.2 and said lens system includes an aperture stop located
approximately at the center of said lens system and a plurality of lens
elements centered on an optical axis and arranged into two lens groups of
positive power to provide said high numerical apertures on both object and
image sides of said lens system.
7. An imaging apparatus comprising:
means for supporting an imaging member that is to receive an exposure;
means for generating a light beam;
means for projecting said light beam onto said member, wherein said light
projection means includes a finite conjugate lens system having high
numerical apertures on both object and image sides comprising an aperture
stop located approximately at a center of said high aperture lens system
and a plurality of lens elements centered on an optical axis and arranged
into two lens groups of positive power to provide said high numerical
apertures on both object and image sides of said lens system, one of said
lens groups being located on one side of said aperture stop and another of
said lens groups located on another side of said aperture stop, said lens
groups each comprising an outer-most lens element and an inner-most lens
element located in close proximity to said aperture stop, said inner-most
lens element of each lens group having a convex surface facing towards
said aperture stop.
8. The imaging apparatus of claim 7 and wherein said numerical apertures
are at least 0.2.
9. The imaging apparatus of claim 8 and wherein said numerical aperture on
the image side is at least 0.5.
10. The imaging apparatus of claim 7 and wherein said numerical apertures
are about 0.2 or larger.
11. The imaging apparatus of claim 10 and wherein said numerical aperture
on the image side is about 0.5 or larger.
12. A thermal imaging apparatus comprising:
an imaging drum arranged to mount a receiver member and a donor member in
superposed relationship thereon;
means for rotating the drum about an axis;
means for generating a plurality of modulated coherent light beams;
light projection means for projecting said light beams onto said donor
member to transfer an image onto said receiver member by transfer of a dye
from said donor member; and
wherein said light projection means includes a fiber array, a laser diode,
and a finite conjugate lens system having high numerical apertures of at
least about 0.2 on both object and image sides and said lens system
includes an aperture stop located approximately at the center of said lens
system and a plurality of lens elements centered on an optical axis and
arranged into two lens groups of positive power to provide said high
numerical apertures on both object and image sides of said lens system.
13. The imaging apparatus of claim 12 and wherein said numerical aperture
on the image side is 0.5 or larger.
14. A thermal imaging apparatus comprising:
an imaging drum arranged to mount a receiver member and a donor member in
superposed relationship thereon;
means for rotating the drum about an axis;
means for generating a plurality of modulated coherent light beams;
light projection means for projecting said light beams onto said donor
member mounted on said drum member to transfer an image onto said receiver
member by transfer of a dye from said donor member; and
wherein said light projection means includes a fiber array, a laser diode
and a finite conjugate lens system having high numerical apertures on both
object and image sides, an aperture stop is located approximately at the
center of said lens system and a plurality of lens elements are centered
on an optical axis and arranged into two lens groups of positive power to
provide said high numerical apertures on both object and image sides of
said lens system, one of said lens groups being located on one side of
said aperture stop and another of said lens groups being located on
another side of said aperture stop, said lens groups each comprising an
outer-most lens element and an inner-most lens element located in close
proximity to said aperture stop, said inner-most lens element of each lens
group having a convex surface facing towards said aperture stop.
15. An imaging apparatus comprising:
means for supporting an imaging member that is to receive an exposure;
means for generating a light beam;
means for projecting said light beam onto said member, wherein said light
projection means includes a fiber array and a finite conjugate lens system
having high numerical apertures on both object and image sides for imaging
said fiber array, said lens system comprising an aperture stop located
approximately at the center of said high aperture lens system and a
plurality of lens elements centered on an optical axis and arranged into
two lens groups of positive power to provide said high numerical apertures
on both object and image sides of said lens system for relating said fiber
array to the imaging plane, one of said lens groups being located on one
side of said aperture stop and another of said lens groups located on
another side of said aperture stop, said lens groups each comprising an
outer-most lens element and an inner-most lens element located in close
proximity to said aperture stop, said inner-most lens element of each lens
group having a convex surface facing toward said aperture stop.
16. The imaging apparatus of claim 15 and wherein said numerical apertures
are at least 0.2.
17. The imaging apparatus of claim 16 and wherein said numerical aperture
on the image side is at least 0.5.
Description
BACKGROUND OF THE INVENTION
Related Applications
The present application is related to the following commonly assigned
co-pending applications: U.S. Ser. No. 670,088, U.S. Pat. No. 5,146,242
entitled WRITING BEAM ANGULAR ALIGNMENT DEVICE; U.S. Ser. No. 670,089,
U.S. Pat. No. 5,146,241 entitled AUTOMATIC CUT-OUT FOR AUTO-FOCUS DEVICE;
U.S. Ser. No. 670,092, U.S. Pat. No. 5,212,500 entitled WRITING BEAM
FOCUSING UTILIZING LIGHT OF A DIFFERENT WAVELENGTH; U.S. Ser. No. 670,095,
U.S. Pat. No. 5,196,886 entitled FOCUS FIBER MOUNT; and U.S. Ser. No.
670,129, U.S. Pat. No. 5,138,497 entitled HIGH SPEED FOCUSING LENS
ASSEMBLY, all filed on Mar. 15, 1991; and U.S. Ser. No. 749,228, entitled
LASER THERMAL PRINTER METHOD AND APPARATUS, in the names of Raymond J.
Harshbarger, William G. Fahey, Ronald R. Firth, Seung-ho Baek, and Charles
D. DeBoer; U.S. Ser. No. 749,229, entitled LASER THERMAL PRINTER USING
ROLL MATERIAL SUPPLY, in the names of Frederick B. Fox, Michael H. Parsons
and James L. Mohnkern; U.S. Ser. No. 749,378, entitled SELECTIVELY WOUND
MATERIAL FOR A LASER THERMAL PRINTER, in the name of Michael H. Parsons;
U.S. Ser. No. 749,223, entitled MATERIAL SUPPLY CAROUSEL, in the names of
James L. Mohnkern, Michael H. Parsons, and Rene L. Gobeyn; U.S. Ser. No.
749,050, entitled MATERIAL TRANSPORT UTILIZING A MOVABLE EDGE GUIDE, in
the name of Michael H. Parsons; U.S. Ser. No. 749,372, entitled LASER
THERMAL PRINTER WITH A VERTICAL MATERIAL TRANSPORT, in the name of Michael
H. Parsons; U.S. Ser. No. 749,224, entitled MATERIAL TRANSPORT THAT
SELECTIVELY CONTACTS DIFFERENT MATERIALS, in the names of Michael H.
Parsons and William J. Simmons; U.S. Ser. No. 749,399, entitled
MULTI-CHAMBERED IMAGING DRUM, in the name of Roger S. Kerr: U.S. Ser. No.
749,232, entitled METHOD AND APPARATUS FOR SELECTIVELY SORTING
IMAGE-BEARING SHEETS FROM SCRAP SHEETS, in the names of Bradley C. DeCook,
Roger S. Kerr and Richard L. O'Toole; U.S. Ser. No. 749,391, entitled
VACUUM IMAGING DRUM WITH A MATERIAL RECEIVING RECESS IN THE PERIPHERY
THEREOF, in the name of Roger S. Kerr; U.S. Ser. No. 749,231, entitled
METHOD OF REMOVING AIR FROM BETWEEN SUPERPOSED SHEETS, in the names of
Bradley C. DeCook, Roger S. Kerr and Richard L. O'Toole; U.S. Ser. No.
749,389, entitled VACUUM IMAGING DRUM WITH AN AXIAL FLAT IN THE PERIPHERY
THEREOF, in the name of Roger S. Kerr; U.S. Ser. No. 749,230, entitled
METHOD AND APPARATUS FOR LOADING AND UNLOADING SUPERPOSED SHEETS ON A
VACUUM DRUM, in the names of Roger S. Kerr and James K. Lucey; U.S. Ser.
No. 749,227, entitled LASER THERMAL PRINTER WITH POSITIVE AIR FLOW, in the
names of Roger S. Kerr and Douglass L. Blanding; U.S. Ser. No. 749,226,
entitled AUTO-FOCUS DETECTOR MASK, in the name of Michael S. Ferschl; U.S.
Ser. No. 749,225, entitled INITIAL SET-UP PROCEDURE FOR AN AUTO-FOCUS
LENS, in the name of Michael S. Ferschl; U.S. Ser. No. 749,222, entitled
FOCUSING LASER DIODE MOUNT ON A WRITE HEAD, in the names of Michael S.
Ferschl and Erich Zielinski; U.S. Ser. No. 749,386, entitled OPTICAL FIBER
MOUNT AND SUPPORT, in the names of Roger S. Kerr and Stanley J. Thomas;
U.S. Ser. No. 749,387, entitled REGISTRATION INDICIA ON A DRUM PERIPHERY,
in the names of Cheryl J. Kuberka, David F. Dalfonso and Ensley E.
Townsend; U.S. Ser. No. 749,382, entitled PRECISION LEAD SCREW DRIVE
ASSEMBLY, in the name of Erich Zielinski; U.S. Ser. No. 749,390, entitled
OPTICAL FIBER TAKE-UP ASSEMBLY, in the name of Erich Zielinski; U.S. Ser.
No. 749,383, entitled WRITING TRANSLATOR MOUNT, in the name of Erich
Zielinski; and U.S. Ser. No. 749,396, entitled HIGH APERTURE FINITE
CONJUGATE LENS SYSTEM SUITABLE FOR USE AS A MICRO RELAY LENS, in the name
of Donald DeJager, all filed Aug. 23, 1991.
Technical Field
This invention relates generally to thermal printers and more particularly
to a thermal printer with micro relay lens system having high numerical
apertures on both object and image sides.
Background Art
In the graphic arts industry, high dot density, high quality digital
scanning printers are used for color proofing image generation, negative
making or direct digital plate making. Typical required dot densities
range from 1,000 dots per inch up to 3,000 dots per inch. The image sizes
are comparatively large, from A4(8".times.10") to A2(18".times.24").
Printing any images of A2 size at 2,400 dots per inch (DPI) requires the
system to handle 200 Mbytes of data in a few minutes. The size of the
image and the large amount of image data employed makes the laser scanning
system expensive and complicated. Any laser printing system using one
laser beam requires expensive high speed electronics and precision optical
components such as high performance lenses, a high speed polygon mirror or
hologon deflector and complicated control electronics.
Our invention comprises a new simple system using a multiple line scanning
printhead with a unique relay lens system. However, the lens system has to
be a high quality finite conjugate system with high numerical apertures on
both image and object sides. No such system was found to exist.
SUMMARY OF THE INVENTION
The object of this invention is to provide a thermal imaging apparatus
using a multiple line scanning printhead with a very fast relaying lens
system.
Accordingly, our invention comprises a thermal imaging apparatus comprising
an imaging drum member mounted for rotation about its axis and arranged to
receive a receiver member and a donor member superposed on the receiver
member, means for generating a plurality of modulated coherent light
beams, means for projecting the light beams onto the donor member mounted
on the drum member to transfer an image onto the receiver member by
transfer of a dye from the donor member, wherein the light projection
means includes a finite conjugate lens system having high numerical
apertures on both object and image sides and includes an aperture stop
located approximately at the center of the high aperture lens system and a
plurality of lens elements centered on an optical axis and arranged into
two lens groups of positive power to provide the high numerical apertures
on both object and image sides of the lens system.
According to a preferred embodiment of the invention, the thermal printer
finite conjugate lens system includes two lens groups which are located on
each side of the aperture stop and each lens group comprises an outer-most
lens element and an inner-most lens element. The inner lens elements are
located in close proximity to the aperture stop and each of the inner-most
lens elements have a convex surface facing towards the aperture stop.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a profile drawing of an optical system used of the first
illustrative embodiment of the present invention;
FIG. 2 is a schematic of a laser diode thermal printing system of the first
illustrative embodiment;
FIG. 3 is a schematic of a multi-fiber array printing head;
FIG. 4 is a profile drawing of a second optical system;
FIG. 5 is a profile drawing of a third optical system; and
FIG. 6 is a profile drawing representing a fourth and fifth optical system.
BEST MODE FOR CARRYING OUT THE INVENTION
The preferred embodiment of the printer system shown in FIGS. 2 and 3 is
composed of a drum 10, a lead screw 12 and a printhead 14. The
photosensitive or thermal sensitive media 16 is wrapped around the drum 10
and the multiple laser beams are focused on the media 16. The printhead 14
is carried on a rail 18 and is driven by the lead screw 12 in
synchronization with the drum rotation, so that the multiple image lines
are scanned either helically or stepping-stair fashion to cover the whole
imaging area. The optical system of the printer is composed of a silicon
V-grooved fiber array 20, an imaging lens 15 and laser diodes (not shown).
The fiber array 20 and the imaging lens 15 are mounted on a printhead
mount module 14 with other associated components. The printhead module 14
is detached easily for any service as necessary.
It is well known technology that a silicon wafer 13 can be etched to have
V-grooves 17 or U-grooves using chemical etchants. It is also well known
to fabricate a fiber array using the silicon V-grooves 17 and multiple
optical fibers 19. Two patents have been issued on the fiber array
printhead as U.S. Pat. No. 4,389,655 and U.S. Pat. No. 4,911,526. The
printer system can use either method, simple straight- V-grooves as
indicated in U.S. Pat. No. 4,389,655 or tapered fibers in the fanned-out
V-grooves described in U.S. Pat. No. 4,911,526. The silicon wafer is
prepared with many photolithographic patterns to form up to 6 printheads.
The wafer is coated with 100 angstroms of silicon oxide and another 100
angstroms of silicon nitride to prevent undercutting of the masked area.
When the depth of V-grooves are more than a few 10's of microns, the
silicon wafer has to be etched longer periods, which tends to etch under a
narrow stripe of masked area. This undercutting of the masked area makes
it difficult to have deep V-grooves with a very narrow gap between. The
silicon nitride helps to protect the narrow masked area due to the very
dense protective mask. We added 100 angstrom of silicon nitride on the top
of the silicon oxide layer which is the typical practice in the industry.
The etchant is a solution of 20% KOH, 64% water and 16% of Isopropanol by
weight at 50 degree C. The isopropanol also helps to prevent the
undercutting problem of the narrow masked area.
A single layer, multi-fiber array printhead on a silicon wafer provided
with V-grooves is used with a lens to achieve small written dot size on
the order of 10 .mu.m diameter or less than 10 .mu.m. The lens can reduce
the diameter of the image of the fibers to 1/2 to 1/3 of the original
size. If small diameter, multimode fibers, such as 50 .mu.m core, or a
single mode fiber with 10 .mu.m core are used, very small written dot
sizes required for high dot density-high quality imaging printing may be
obtained. The specific lenses will be discussed in the following section.
According to one aspect of the present invention, several lines are
written helically or stepping-stair fashion to cover the whole width of
the image. If an overlap is required to cover the raster lines, the
printhead is tilted to the proper angle to the drum axis.
To relate a large number of fibers to the imaging plane, very unusual lens
systems have been designed. The requirements for the lens system are;
a) It must have a large covering area on the focal planes. Typical required
focal area is 2 mm on the object focal plane and 1 mm or 0.7 mm on the
imaging focal plane.
b) They have high numerical apertures, on both object and image sides, such
as are associated with microscope objectives. The numerical aperture on
the object side of the lens should be large enough to capture a large
fraction of the energy leaving the fiber ends. Multimode fibers typically
have numerical apertures of 0.3 to 0.4, and single mode fibers will
typically have numerical apertures of 0.1 to 0.2. The relay lenses
described herein have object-side numerical apertures of 0.2 to 0.253,
which is large enough to capture most of the energy emitted by the fibers.
The magnification of the lens is determined as;
##EQU1##
Five different lens systems were designed to be used with the printing
system. Their system parameters are described below in the following five
embodiments:
______________________________________
Embodi-
ment
number 1 2 3 4 5
______________________________________
Number of
7 8 8 9* 9*
Elements
Object 3.6 mm 3.6 mm 2.4 mm 3.6 mm 3.0 mm
Diagonal
Image 1.8 mm 1.2 mm 0.8 mm 1.68 mm
1.4 mm
Diagonal
Magnifica-
0.5 0.3333 0.3333 0.46 0.46
tion
Object 0.25 0.2 0.2 0.253 0.253
Numerical
Aper.
Image 0.50 0.6 0.6 0.55 0.55
Numerical
Aper.
ANSI f- 0.67 0.63 0.63 0.62 0.62
number of
lens
Total 50.8 mm 50.8 mm 50.8 mm
70.7 mm
58.5 mm
Track
Length
______________________________________
*not including the beamsplitter prism used for autofocusing.
Any optical component should be properly mounted without any loose
movement. We discovered a novel printhead mount module which holds the
printhead in a rotational printhead holder with an accurate focus adjuster
and the relaying lens on the same mount. The module ensures that there is
no loose movement between each of the components and it is easy to
service. The printhead is held firmly in a holder which sits in a barrel
type focusing adjuster moving along the optical axis. The focusing
attachment is held firmly in a rotational stage which can be rotated very
accurately by 0.1 degree graduations. A shutter is attached between the
printhead and the lens, so that the writing beams are blocked as
necessary. The relaying lens is held firmly on the mount. Whenever the
lens has to be cleaned, the whole mount can be detached from the printing
system and the lens can be cleaned or serviced easily.
Each end of the fibers of the printhead is terminated using standard
connectors, such as ST or SM connectors. The laser diodes with fiber
pig-tails are terminated using the same type of standard connectors and
the two ends from laser diodes and fibers of the printhead are connected
easily. It is very easy to replace any laser diodes which are degraded or
dead. The laser diodes can be mounted away from the thermally sensitive
mechanical or optical components of the printer and can be cooled using an
inexpensive fan or some other means.
The lens system 100 is illustrated in FIG. 1. It was designed for use in a
laser thermal printing system (FIG. 2) using a multi-fiber array printing
head (FIG. 3) coupled to high power laser diodes. The printer system uses
a drum for the line direction scan movement and a stepping motor or a
linear translation stage for the page direction scan movement. A custom
designed lens was necessary to meet the requirements for the numerical
aperture and the field of view requirements. The numerical aperture of the
beam on the object side of the lens system is 0.25, and the numerical
aperture of the beam on the image side of the lens system is 0.5. The ANSI
f-number of the lens system is 0.6667. The field angle is 3.08 degrees.
The relative illumination due to cosine effects exceeds 1.0 at the edge of
the field of view. The distance from the object to image is 50.8 mm (2
inches). The lens system 100 is used in the rear infrared IR (630 to 810
nm) to relay an object having a diameter of 2.4 mm to an image of diameter
1.2 mm giving a magnification of 1/2. The lens system is used to form an
image of a source consisting of a linear array of fibers, each
transmitting energy from remotely located infrared laser diodes. The
combination of very high numerical aperture and sharp imagery over an
extended field of view dictated the need for a new lens of a very unusual
construction.
The lens system 100 comprises a plurality of lens elements and an aperture
stop located approximately at the center of the lens system. Following
from object to image, the numerical data for the optical system is as
follows:
TABLE 1
______________________________________
CLEAR THICK-
SURFACE APER. RADIUS NESS GLASS
______________________________________
S1 8.41 38.6019 3.670 5l7642
S2 8.82 -7.29740 4.100
S3 6.83 -4.31940 2.360 785258
S4 8.94 -8.54580 1.400
S5 10.12 PLANO 6.290 651559
S6 11.36 -10.7207 0.500
10.55 DIAPHRAGM 0.500
S7 10.44 17.0410 3.800 651559
S8 9.87 -12.0819 1.500 785258
S9 9.09 9.22950 1.810
S10 9.57 42.9968 3.020 651559
S11 10.01 -14.6843 0.500
S12 9.74 6.77130 6.400 720504
S13 5.98 15.7111 1.000
S14 5.14 PLANO 1.000 517642
S15 4.44 PLANO
LENS LENGTH 37.850
______________________________________
The lens system 200 is illustrated in FIG. 4, and is used to relay an
object of a diameter 3.6 mm to an image of diameter 1.2 mm giving a
magnification of 1/3. The numerical aperture of the optical system at the
object side is 0.2. The numerical aperture of the optical system at the
image side is 0.6. The ANSI f-number is 0.625. This lens system is
designed for possible use as a 1/3 X relay lens in a laser thermal printer
described in FIGS. 2 and 3. The lens system 200 comprises a plurality of
lens elements arranged into two lens groups on either side of the aperture
stop. The aperture stop is again located approximately at the center of
the lens system. The numerical data for the optical system of 200 is as
follows:
TABLE 2
______________________________________
CLEAR THICK-
SURFACE APER. RADIUS NESS GLASS
______________________________________
S1 8.35 -10.7207 2.970 651559
S2 9.42 -7.32390 0.580
S3 8.87 18.1807 3.070 651559
S4 8.22 -18.1807 1.650
S5 7.65 -5.62700 3.070 785258
S6 9.41 -96.0144 5.000 651559
S7 10.75 -8.52190 0.500
9.92 DIAPHRAGM 0.500
S8 9.76 11.9221 3.140 651559
S9 8.92 PLANO 1.500 785258
S10 7.88 6.67350 1.340
S11 8.13 18.1807 3.070 651559
S12 8.33 -18.1807 0.500
S13 7.97 5.91100 3.580 720504
S14 6.40 PLANO 0.500
S15 5.61 PLANO 1.000 517642
S16 4.72 PLANO
LENS LENGTH 31.970
______________________________________
On the image side of the lens system, there is a 1 mm thick protective
window, which can be easily cleaned. The focusing function is performed by
moving an entire lens system.
The lens system 300 is illustrated in FIG. 5. It is designed for the
wavelength range of 750 to 850 nm with the principal wavelength of 800 nm.
The focusing function is performed by the movement of the rear-most lens
element L8. The track length (i.e. the distance from the object to the
image), nominally 2 inches or 50.8 mm will thus change by .+-.0.1 mm.
Unlike the above two lens systems, this lens system does not use a
protective window at the rear. The object diameter is 2.4 mm, while the
image diameter is 0.8 mm, thus the optical system 300 has a magnification
of 1/3. The numerical aperture at the object side is 0.2 and the numerical
aperture at the image side is 0.6. The lens system 300 has an unusual
feature, its sixth lens component can be varied in position, with respect
to the preceeding components, by as much as +/-0.1 mm, while the location
of the image surface will stay nearly fixed with respect to the rear plano
surface of sixth component.
The object for the lens system 300 consists of a linear array of 15
circular spots, each 0.1 mm in diameter, with center to center spacing of
0.15 mm. At 1/3 magnification, the images of the spots are 0.0333 mm in
diameter. This is relative coarse image structure.
Because of the high numerical aperture of the beam at the image, the depth
of focus according to the Rayleigh criterion is about +/-0.00111 mm, but
because of the relatively coarse nature of the image structure, a more
realistic tolerance for the depth of focus is about +/-0.01 mm, about 9
times larger than the Rayleigh depth. The numerical data for the lens
system 300 is as follows:
TABLE 3
______________________________________
CLEAR THICK-
SURFACE APER. RADIUS NESS GLASS
______________________________________
S1 7.31 -11.7310 3.060 651559
S2 8.35 -7.21870 0.500
S3 8.06 24.8075 2.970 651559
S4 7.61 -15.0074 1.510
S5 7.19 -5.20670 3.910 785258
S6 9.77 42.2210 4.870 651559
S7 11.03 -8.23800 0.500
10.34 DIAPHRAGM 0.500
S8 10.14 10.9567 3.260 651559
S9 9.21 PLANO 1.500 785258
S10 7.97 6.38860 1.360
S11 8.23 15.0074 2.970 651559
S12 8.33 -24.8075 1.100
S13 7.94 6.19740 3.500 772497
S14 6.40 PLANO
LENS LENGTH 31.510
______________________________________
The fourth and the fifth lens systems that may also be used in the printer
apparatus are similar to each other and are illustrated in FIG. 6.
They are designed to have a track length of 70.7 m and 58.5 mm
respectively. The object side numerical aperture is 0.253. The image side
numerical aperture is 0.55. The ANSI f-number is 0.62 and magnification is
0.46 for both lens system designs.
Both lens systems are designed for 750-850 nm range and are given in Tables
4 and 5.
TABLE 4
______________________________________
CLEAR THICK-
SURFACE APER. RADIUS NESS GLASS
______________________________________
S1 6.92 PLANO 12.000 785258
S2 10.65 PLANO 4.000
S3 12.40 -21.6194 3.020 772497
S4 13.39 -11.1939 3.860
S5 13.01 24.0092 2.000 785258
S6 12.11 9.35980 5.500 772497
S7 11.36 -32.6195 4.430
S8 8.62 -6.61220 4.400 785258
S9 10.81 PLANO 5.910 772497
S10 12.29 -10.9567 0.320
11.43 DIAPHRAGM 0.300
S11 11.25 41.0008 3.370 772497
S12 10.47 -34.0226 2.000 785258
S13 8.76 7.07690 2.220
S14 9.21 32.7992 2.170 772497
S15 9.39 -32.7992 1.100
S16 9.34 7.29740 3.500 772497
S17 8.12 PLANO
LENS LENGTH 60.100
______________________________________
TABLE 5
______________________________________
CLEAR THICK-
SURFACE APER. RADIUS NESS GLASS
______________________________________
S1 4.83 PLANO 8.000 517642
S2 7.73 PLANO 4.000
S3 9.63 -18.9706 3.360 772497
S4 10.85 -9.27810 1.240
S5 10.56 32.8590 2.000 785258
S6 10.05 11.1065 4.790 772497
S7 9.47 -22.3953 4.380
S8 6.95 -5.06210 3.000 785258
S9 9.01 98.0453 5.060 772497
S10 10.49 -8.74010 0.550
9.80 DIAPHRAGM 0.420
S11 9.75 11.9576 3.690 772497
S12 8.89 -20.9492 2.000 785258
S13 7.42 6.11100 1.870
S14 7.88 23.8064 2.680 772497
S15 8.13 -23.8064 1.100
S16 7.99 6.19740 3.500 772497
S17 6.56 PLANO
LENS LENGTH 51.640
______________________________________
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